1. Field
Aspects of embodiments of the present invention relate to a display device, and more particularly, to a chip on plastic (COP) type display device.
2. Description of the Related Art
Embodiments of the present invention are directed to a liquid crystal display (LCD) device, in more particular, to a COP type LCD device.
The LCD device may display image information utilizing an electro-optical property of liquid crystal molecules injected into a liquid crystal panel provided therein. The LCD device may be advantageous over electronic products including a cathode ray tube (CRT) in that it has low power consumption, light weight, and a small volume. Accordingly, the LCD device may be used in a wide range of applications, such as a display device of a portable computer, a monitor of a desk top computer, and a monitor of an image display device displaying a high-definition image.
The LCD device may be generally divided into an LCD panel assembly and a backlight assembly. The LCD panel assembly may include: an LCD panel formed by injecting liquid crystal materials having dielectric anisotropy between a thin film transistor (TFT) substrate and a common electrode substrate; driving chips applying driving signals to each of a gate line and a data line formed on the LCD panel; a printed circuit board transmitting data (e.g., predetermined data) and control signals to the driving chip, and a flexible printed circuit board connecting driving chips to each other. The LCD panel assembly may be coupled to the backlight assembly, which includes a lamp assembly and various optical sheets, to thereby constitute an LCD device.
On the TFT substrate of the display panel there may be a gate pad for receiving a scan voltage from the driving chip, a gate wiring including a gate line and a gate electrode for transmitting the scan voltage, a data pad for receiving a signal voltage from the driving chip, and a data wiring for transmitting a data voltage to a pixel electrode through a source electrode and/or a drain electrode. On the gate line and the data line, the pixel electrode is formed for each pixel, and the TFT connected to the gate line, the data line, and the pixel electrode may be formed for each pixel.
In order to connect the gate pad and the data pad of the TFT display panel to the driving chip, a bump, which may be respectively connected to the gate pad and the data pad, is formed on a chip pad of the driving chip.
The driving chips formed with the bump may be respectively connected to the gate pad and the data pad in the following manner: an electrode of the driving chip disposed outside of the LCD panel may be connected to a pad of an insulating substrate provided in the gate pad and the data pad, using a film attached with a metal line in a tape automated bonding (TAB) method; or the driving chip may be directly mounted on the insulating substrate in a chip on glass (COG) method.
Herein, in the COG method, the driving chip may be attached to the insulating substrate only using the bump of the driving chip and an anisotropic conductive film (ACF).
However, in the COG method, organic insulating layers and the like are stacked as a protection layer so as to protect a driving element such as a TFT of an organic light emitting diode (OLED) display device, and thus compression defects may occur when connecting a bump and the like to a pad unit due to a step difference between the pad unit, below which a metal layer is disposed, and portions apart from the pad unit.
In particular, recently, a flexible OLED display device has drawn attention as a flat panel display device of the next generation, which is made of a flexible material, such as a flexible glass substrate or plastic, and is capable of performing its display function even when being bent like a piece of paper.
In a case where the flexible OLED display device retains its curved shape, however, a crack may appear on the insulating layer protecting the TFT, thus causing a defect in the driving element.
It is to be understood that this background of the technology section is intended to provide useful background for understanding the technology and as such disclosed herein, the technology background section may include ideas, concepts or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to a corresponding effective filing date of subject matter disclosed herein.